According to a McDonald’s Cyclospora outbreak update issued by the U.S. Centers for Disease Control and Prevention (CDC) late last week, food poisoning cases have been confirmed in at least 15 states.

The outbreak was first announced by the CDA and the Food and Drug Administration (FDA) on July 13, after at least 61 laboratory-confirmed cases of Cyclospora infections were identified among individuals who reported eating salads from McDonald’s restaurants within a week prior to their illness onset date.

Since the initial announcement, federal officials have performed epidemiologic and trace back investigations in search of the source of the contamination. To date, officials have identified the romaine lettuce and carrot mix distributor, Fresh Express, as the likely source of the outbreak.

Further investigations determined that Fresh Express distributes produce to more than 3,000 McDonald’s restaurants across 14 states, including Illinois, Minnesota, Montana, Nebraska, South Dakota, Wisconsin, Indiana, Michigan, Ohio, North Dakota, Kentucky, West Virginia, and Wisconsin.

On July 30, the U.S. Food Safety and Inspection Service (FSIS) issued a public health alert warning individuals to refrain from consuming pre-made salads and wraps containing romaine lettuce that were distributed by Caito Foods LLC, of Indianapolis, Indiana, which is Fresh Express’ distributor to McDonald’s restaurants.

Cyclospora is a parasitic infection that can cause severe intestinal illness. It is only spread through human waste, unlike E. coli and salmonella. Common symptoms include loss of appetite, weight loss, stomach cramps, bloating, increased gas, nausea, and fatigue. Some patients also experience vomiting, body aches, headache, low-grade fever, and other flu-like symptoms.

Many people who are infected experience no symptoms and it is rarely lethal. Symptoms may last from a few days to a few months. At times, a person may seemingly become better, only to experience a relapse of the illness.

Cyclospora is not routinely tested for in doctor’s offices or laboratories. Consumers who think they may be ill or have been exposed should talk to their doctor so a specific test can be run.

Officials are advising consumers if they have purchased one of the pre-made salads or wraps and have not eaten it yet, to discard it or return it the place of purchase. Customers who have eaten the pre-made salads or wraps that have experienced symptoms of diarrhea, to see their healthcare provider as soon as possible.

The CDC announced the investigation is still ongoing and will be working with the FDA, FSIS and all involved parties to stop further spread of contamination and that updates will be released as information is obtained.